Hub 3 / Compal CH7465-LG (TG2492LG) and CGNV4 Latency Cause

[Datalink]

Good Day Ladies and Gentlemen,

Greetings from the other side of the pond, so to speak.  Over the last few weeks I've been perusing various user forums across North America and Europe for issues related to Intel Puma 6 modem latency.  Of those forums, your Hub 3 stands out as yet another Puma 6 based modem where users see continuous latency no matter what site is used or what online game is played. Considering all of the problems that are on the go, the following information should be of interest to all Hub 3, Compal CH7465-LG and Hitron CGNV4 modem users.  There is much more to post regarding this, so this is a start, to alert VM users as to the real cause of the latency and hopefully engage the VM engineering staff, via the forum staff, with Arris.  I am surprised to see that there has been no mention on this board of users from other ISPs who are suffering the exact same issues with their modems, so, this may come as a surprise to some, and possibly old news to others.

So, the short story ........

The Hub 3 / Compal CH7465-LG (TG2492LG) & Hiton CGNV4 modems are Intel Puma 6 / 6 Media Gateway (MG) based modems.  These modems exhibit high latency to the modem and high latency thru the modem.  The latency affects all IPV4 and IPV6 protocols, so it will be seen on every internet application and game.  The basic cause is the processing of the data packets thru a CPU software based process instead of thru the hardware processor / accelerator.  It appears that a higher priority task runs periodically, causing the packet processing to halt, and then resume.  This is observed as latency in applications and in ping tests to the modem and beyond.  For the last several weeks, Hitron, along with Intel and Rogers Communications in Canada have been addressing the latency issue within the Hitron CGNxxx series modems.  To date, only the IPV4 ICMP latency has been resolved.  Although this is only one protocol, it does show that a Puma 6MG modem is capable of using the hardware processor / accelerator with good results.  Currently Rogers is waiting for further firmware updates from Hitron which should include an expanded list of resolved protocol latency issues.  For Arris modems, "Netdog" an Arris engineer indicated last week that Arris was onboard to address the issue for the Arris SB6190 modem.  That should be considered as good news for any Arris modem (read Hub 3) user as Arris should be able to port those changes over to other Puma 6/6MG modems fairly quickly.  This is not a trivial exercise and will probably take several weeks to accomplish.  Note that there is no guarantee at this point that it is possible to shift all packet processing to the hardware processor / accelerator without suffering from any packet loss side effects.  Time will tell if all of the technical issues can be resolved with the current hardware included in the Puma 6/6MG chipset.  Last night, Netdog loaded beta firmware on selected test modems on the Comcast Communications network.  As this was only done last night, it's too soon to tell what this version resolves and if it was successful or not.  Netdog has contacts with staff at Comcast, Rogers, Charter and Cox Communications to fan out beta versions and modifications for testing.  I'd say its time to add Virgin Media and/or Liberty Global to that group as well.

Recent activity:

Approx three weeks ago a DSLReports user, xymox1 started a thread where he reported high latency to an Arris SB6190 and illustrated that with numerous MultiPing plots.  This is the same latency that I and other users with Rogers communications have been dealing with for months so it came as no surprise.  As well as reporting via that thread, xymox1 took it upon himself to email several staff members at Arris, Intel, Cablelabs and others.  The result of that campaign was Netdog's announcement, last week, that Arris was fully engaged at resolving the issue.  That has led to last nights release of beta firmware, although as I indicated its too early to determine what the beta firmware resolves, if anything.

The original thread that xymox1 started is here:

https://www.dslreports.com/forum/r31079834-ALL-SB6190-is-a-terrible-modem-Intel-Puma-6-MaxLinear-mis...

Yesterday, DSLReports issued a news story covering the thread:

https://www.dslreports.com/shownews/The-Arris-SB6190-Modem-Puma-6-Chipset-Have-Some-Major-Issues-138...

Today, Arris responded:

https://www.dslreports.com/shownews/Arris-Tells-us-Its-Working-With-Intel-on-SB6190-Puma6-Problems-1...

That response was also picked by Multichannel.com

http://www.multichannel.com/news/distribution/intel-arris-working-firmware-fix-sb6190-modem/409379

This is more news likely to appear in the next few days as additional tech and news staff pick up on this issue.

Hub 3 observations:

Like many others using a Puma 6/6MG modem, Hub 3 users are experiencing latency when they ping the modem, or ping a target outside of the home, game online or use low latency applications.  The common misconception is that this is Buffer Bloat. It's not. Its most likely a case of the packet processing stopping while the CPU processes a higher priority task.  The packet processing is done via the CPU no matter what mode the modem is operating in, modem mode or router mode and no matter what IPV4 or IPV6 protocol is used.  Normally, the latency is just that, latency.  The exception are UDP packets. In this case there is latency and packet loss.  The result of that is delayed and failed DNS lookups, and poor game performance for games that use UDP for player/server comms or player/player comms.

Can this be fixed?

So far, it appears that the answer is yes.  Rogers Communications issued beta firmware to a small group of test modems in October.  This version shifted the IPV4 ICMP processing from the CPU to the hardware processor / accelerator, resulting in greatly improved performance in ping latency.  At the present time we are waiting for the next version firmware which should shift other protocols over to the hardware processor / accelerator.  That can be seen in the following post:

http://communityforums.rogers.com/t5/forums/forumtopicpage/board-id/Getting_connected/message-id/369...

The details and results of last nights beta release to the Comcast group have yet to be seen.

At this point there is enough reading to keep most staff and users busy.  My intention is to post some of the history leading up to this point and instructions on how to detect the latency and packet loss.  This is not thru the use of a BQM.  I had hoped to post this all at once but events are moving much faster than I had thought they would.  For now this should suffice to get the ball rolling.

Below is a link to a post with a couple of HrPing plots from my 32 channel modem to the connected CMTS.  This shows the latency that is observed and reflects what others have posted in this forum using Pingplotter and HrPing.

https://www.dslreports.com/forum/r31106550-

HrPing is one of the freebie applications that can be used to monitor the latency to and thru the modem. 

Pingplots with Pingplotter which show the latency from my modem to the CMTS can be found in the first two to three rows of my online image library at Rogers Communications, located below.  They are essentially what the BQM would look like if you were able to zoom into the plot to the point where you could see the individual ping spikes.  Those ping spikes are common to Puma 6 and Puma 6MG modems.

http://communityforums.rogers.com/t5/media/gallerypage/user-id/829158

 [MOD EDIT: Subject heading changed to assist community]

[philjohn]

I know the R7800 has had some issues with latency spikes, although the latest Linux Kernel seems to fix this (running OpenWRT Master)

[nad223]

its called bt homehub 4

[CJS23]

Best site I've found for info on the whole debacle is here

http://www.badmodems.com/

[Mikey86uk]

So its still not safe to upgrade from my ancient Super Hub 1 on VIVID 100 to the Super Hub 3 and VIVID 350?

Im a heavy user who games and streams Netflix (upto 4K) and stream 4K movies from iTunes, and with my Sky Q box downloading in the background at times I need the higher package really, but really don't like the sound of the Super Hub 3! 

It would be used in Modem mode and connected to my Netgear R7000 router, but I don't think that makes any difference with the Hub 3? 

[jonathanm]

For all the things you describe (other than gaming) the Hub 3.0 even on the current/old (9.1.116V) should be more than adequate for those activities. Gaming is where there is a bit more of a risk, if you went to VIVID 350 and got the latest firmware (.603) then the recent posts suggest that this is better (dare I say seemingly on par with previous hubs?).

I'm on VIVID 200 and have a Hub 3.0 and don't have any issues with streaming or downloads.

Guess it depends what's more important or would hurt more - more bandwidth vs the risk of now getting the latest firmware for a some undetermined amount of time.

This assumes that there are not non-hub related connection issues when/if you upgraded - which I guess is a risk regardless of whether it was the Hub 3.0 or another version.

[philjohn]

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@Mikey86uk wrote:

Im a heavy user who games and streams Netflix (upto 4K) and stream 4K movies from iTunes, and with my Sky Q box downloading in the background at times I need the higher package really, but really don't like the sound of the Super Hub 3! 

The Puma 6 issue is somewhat overblown, insofar as for the things you state are important (bar gaming) it makes zero difference. Some people have stated their browsing was stalling, but that's not something I encountered, perhaps because a lot of the issues with UDP packet loss and jitter could lead to DNS lookups failing. I have a caching DNS resolver on my own network which keeps 65k DNS entires locally, so lookups are sporadic.

It's likely if you upgrade to Vivid 350 you'll get .603 from inferring that other people on 350 are the ones who have had the update pushed when doing a reset, and from me being upgraded to it when I went from Vivid 200 to 350.

The other thing to think about is - do you *really* need 350Mbps? 4K netflix is circa 15Mbps, iTunes is similar bitrate. Sky Q will be ever so slightly higher - but - these are all "bursty" and so having sustained speed you're not using is just wasting money.

[Andrew-G]

Mikey86uk: "Im a heavy user who games and streams Netflix (upto 4K) and stream 4K movies from iTunes, and with my Sky Q box downloading in the background at times I need the higher package really, but really don't like the sound of the Super Hub 3! "

Really, you're doing that much downloading?  Gaming won't exceed 1 Mbps download, and that's being exceptionally generous.  Even streaming at 4K is "only" about 15 Mbps.  So if you are gaming and simultaneously watching a 4K download, meanwhile the missus is streaming TWO 4K movies at the same time you're still only using 46 Mbps - on a 100 Mbps contract that leaves your Sky Q with 54 Mbps for background downloads (which as a background task shouldn't really be using more than say 10 Mbps)..  

VM are very keen to flog 350 Mbps because they can charge more, and its faster than the most common form of competition (Openreach VDSL), but very, very few residential customers make any worthwhile use of it.

[Mikey86uk]

I probably don’t need it but VM are offering me the 350 for less than what I’m paying for just the 100, I’m not sure what they would offer with the 200, and even then I think I’m correct in saying that the Super Hub 1 can’t do anything higher than 100? 

I did cancel my 350 order once I found this thread a few weeks ago as I didn’t want the headache with the Hub 3. 

Also so when I cancelled the 350 offer they couldn’t give me any kind of offer with my Vivid 100 package. 

[Andrew-G]

"VM are offering me the 350 for less than what I’m paying for just the 100"

Fair enough, take it with both hands! 

But don't forget that when they start ramping the cost up again, you might be able to cope with a good Openreach connection!  My somewhat cynical view of the 200 and 350 offers is that they cost VM no more to provide than 50 or 100, but VM know that once they've got customer firmly beyond the speeds of Openreach, most people wouldn't willingly revert to a nominally slower line.  At the 50-100 speeds they have to be careful because the market price is largely set by Openreach.  Once they've got customers hooked on higher speeds, then they may not have to worry so much when working out the price rises.

[Datalink]

@philjohn, the fact that you use a caching DNS resolver on your network results in very minimal impact, if any on your web browsing.  GRC's DNS benchmark can show up to a 10 % loss in DNS lookups, and the anecdotal comments from Puma 6 users who have switched to a Broadcom modem indicate that there is a noticeable web cruising improvement with the Broadcom or non-Puma 6 modems.  Speed in this case is irrelevant, its simply a matter what you're attempting to do, if for example you happen to be web cruising when the constant 1.92 second (interval) task runs, stopping traffic thru the modem (latency) and causing UDP losses (most likely due to the UDP packets timing out within the modem).  This should be easy to confirm with Wireshark.